This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The proposed project to be conducted under the guidance and training provided by Dr. Kent Teague at OU-Tulsa is a continuation of one of his current projects. It is primarily focused on further characterization of human thymocyte development and subsequent comparison with data already acquired regarding mouse thymocyte development. Dr. Teague has been able to obtain thymic samples from pediatric thymus cases that can first be sorted and assayed for cell surface receptors such as the TCR, CD4, CD3, and CD8 markers using flow cytometry to determine their developmental stage. Then, these sorted cell populations can be examined for differences in gene expression (such as cytokines) using microarrays and real-time PCR techniques. Preliminary data indicates some distinct differences between the human and mouse systems, such as cellular responses to key cytokine signaling pathways as in IL-7. Traditionally, the mouse model system has been the primary tool used in understanding human immunological responses, but these recent comparisons are indicating that some important differences may exist. These studies are extremely important in understanding T cell development, which is vital to elucidating the mechanisms behind certain diseases affected by T cells such as leukemia, autoimmunity, and loss of T cell function. This information can also be used in stem cell studies in which researchers are attempting to guide development and differentiation pathways. Please note that Dr. O'Farrell is a professor during the school year at Oral Roberts University. She spent the summer working at OU Health Sciences Center, Tulsa with Dr. Teague on this project. Since the institutional profile numbers of both the Tulsa and Oklahoma City locations of OU Health Sciences Center are combined, Dr. O'Farrell's location is listed as University of Oklahoma Health Sciences Center.